This invention relates to a CMOS integrated circuit and, more particularly, to a self-aligned SiGe HBT BiCMOS on a SOI substrate, and a method of fabricating the same.
Conventional fabrication steps for manufacturing Silicon Germanium (SiGe) bipolar complementary metal oxide semiconductor (BiCMOS) devices include fabricating complementary metal oxide semiconductors (CMOS) and SiGe bipolar hetero-junction bipolar transistors (HBT) on a bulk silicon substrate. This process produces a very high performance HBT for analogue signal processing wherein the CMOS portion is used for digital signal processing and data storage. A problem with this state-of-the-art structure is that the bulk CMOS is relatively slow and consumes a relatively large amount of power. The fabrication process for the device is also complex.
By integrating SiGe HBT into silicon-on-insulator (SOI) substrates one can retain the performance of the SiGe HBT and the low power, high-speed properties of a SOI CMOS. Such devices, and processes of manufacturing the same, have been disclosed in U.S. patent application Ser. No. 09/649,380, filed on Aug. 28, 2000 and titled xe2x80x9cMethod of Fabricating High Performance SiGe HBT BiCMOS on SOI Substrate,xe2x80x9d wherein the entire disclosure of said patent application is hereby incorporated by reference. In this patent application, however, the disclosed base/collector junction is not self-aligned. Accordingly, the speed of the device disclosed in the patent application is relatively slow.
The present invention provides a SiGe HBT BiCMOS on a SOI substrate, and a method of fabricating the same, including a self-aligned base/collector junction to optimize the speed of the HBT. The disclosed SiGe BiCMOS/SOI device has a higher performance than a SiGe BiCMOS device on a bulk Silicon substrate. The disclosed device, and method of fabricating the same, also retains the high performance of a SiGe HBT and the low power, high-speed properties of a SOI CMOS. In addition, the disclosed method of fabricating a self-aligned base/collector junction provides a HBT transistor having an improved frequency response.
Accordingly, an object of the invention is to provide a SiGe HBT BiCMOS on a SOI substrate that retains the high performance of a SiGe HBT and the low power, high-speed properties of a SOI CMOS.
Another object of the invention is to provide a SiGe HBT BiCMOS on a SOI substrate including a self-aligned base/collector junction.
A further object of the invention is to provide a SiGe HBT BiCMOS on a SOI substrate having an improved frequency response.